1. Field of the Invention
The present invention relates to a substantially flat aperture-coupled antenna, comprising a multilayer structure with a number of radiating patches arranged on a layer of dielectric material, a corresponding number of apertures, each in the form of two orthogonal slots, in a ground plane layer, and a corresponding number of feed elements in a feed network arranged on at least one planar board for feeding microwave energy from said feed elements, via said orthogonal slots to said radiating patches so as to cause the latter to form a microwave beam propagating from a front side of the antenna, a rear side thereof comprising a metal reflector device.
2. Description of the Invention
Flat aperture-coupled antennas are generally well-known in a variety of embodiments. Compare e.g. the U.S. Pat. Nos. 5,030,961 (Tsao), 5,241,321 (Tsao), 5,355,143 (Zurcher et al), and the European patent application, publ. no. 520908 (Alcatel Espace).
Often, the radiating patches are arranged in a matrix, i.e. a two-dimensional pattern with rows and columns, so that the antenna is extended over a surface area. Alternatively, the antenna may be provided with radiating patches disposed in a vertical row, possibly next to one or more similar antenna elements so as to form a multilobe antenna unit.
In such an antenna structure, including an array or a row of radiating patches and a reflector device at the rear side, there is a technical problem involved in that the reflector device will tend to function as a wave guide. Thus, resonances and an undesired coupling between the various apertures in the matrix will take place. Consequently, the intended beam configuration will be adversely affected, especially with regard to the dual polarization. Also, a substantial portion of the microwave energy fed into the antenna via the above-mentioned network may be lost by way of radiation outside of the forwardly directed beam as well as by heat absorption in the metal reflector device.